Miniaturization Effects and Orientation–Size Interplay in the Fatigue Behavior of AlSi10Mg Produced by Laser Powder Bed Fusion

This study examines build‐orientation and specimen‐size effects on uniaxial fatigue behavior of PBF‐LB AlSi10Mg, with emphasis on the representativeness of miniature specimens. Standard and miniature specimens were fabricated in three orientations and characterized in terms of microstructure, surface roughness, microhardness, and fatigue response. Fatigue failure mechanisms were analyzed, and killer defects were quantified and incorporated into the Murakami model to estimate the effective stress intensity factor (SIF). Unlike the trends commonly reported for AM metals, smaller specimens exhibited increased heat accumulation, resulting in improved surface finish and enhanced fatigue resistance. Miniature specimens consistently outperformed standard ones across orientations, with stronger size dependence in the 45° and horizontal conditions. An orientational anisotropy was observed, with vertical and horizontal specimens outperforming the 45° orientation. Despite the highest surface roughness and initiation defect sizes, horizontal specimens delivered the longest lives overall. SIF estimates indicated greater tolerance to stress concentrations in the horizontal orientation.